U.S. patent application Ser. No. 482,631, filed Apr. 6, 1983, relates to a polyisocyanurate coating composition particularly useful when sprayed in equal volumes as a solid or very high-density foam composition on a substrate, such as a rigid-foam board material, such as rigid polyisocyanurate foam board material. The polyisocyanurate coating composition is prepared by reacting a low-functionality MDI with a polyol composition which comprises a mixture of di or triethylene glycol with a methoxy polyalkylene glycol, such as methoxy polyethylene or polypropylene glycol, the reaction being carried out in the presence of a trimerization catalyst. Optionally, polyether triols may be employed in the polyol composition of the reaction, to increase the impact strength of the resulting cured coating. Some portion of the methoxy polyethylene glycol may be incorporated into the MDI, to provide equal-volume A-side and B-side mixtures, which permits the easy spraying in one-to-one, fixed-volume spray equipment.
U.S. patent application Ser. No. 398,369, filed July 14, 1982, is directed to the preparation of a unique, modified polyisocyanurate foam composition prepared by reacting a low-functionality MDI with from about 5 to 40 parts by weight of a methoxy polyalkylene glycol composition, typically a methoxy polyethylene or polypropylene glycol composition, and with the reaction carried out in the presence of a blowing agent and a trimerization catalyst, to produce a rigid-foam composition having good fire resistance. If desired, the polyol composition employed also may include polyethylene glycol for cost consideration. The polyisocyanurate composition produced is typically characterized by a high compressive strength of about 30 psi or higher, low flame-spread values of 20 or less and low smoke values of about 25 or less.
It is desirable to provide a sprayable polyisocyanurate composition for the spraying of foam and solid coatings. Typically, the foam and coating market for spraying preferentially requires a one-to-one-by-volume system of the A- and B-side components, with the A side comprising the isocyanate or an isocyanate-polyol mixture, and the B side comprising the polyol and its components, such as surfactants, catalysts, blowing agents and the like. It has been found that, when alkoxy polyethylene glycols, such as methoxy polyethylene glycol, are used to form very stiff materials, the stiff materials only can be obtained when the methoxy polyethylene glycol is used in combination with a high isocyanate index, which prevents the popularity of the system in a one-to-one, fixed-spray system. It is, therefore, desirable to provide a modified polyisocyanurate composition, particularly a composition which may be sprayed in fixed, one-to-one volume systems, and which provides for foam and solid coatings of high strength and rigidity and with acceptable fire-performance properties.